Double-ended, double pinch-sealed lamps are usually supplied with bases made of a ceramic sleeve. Metallic connecting elements are located within the sleeve. Usually, the connection contact is disk-shaped, or it may button-shaped or dished. The sleeve, frequently, is slit; the slit is pushed on the pinch seal and retained on the pinch seal by a cement or the like.
It has been found that the use of cement has some disadvantages, particularly if the lamp is subjected to high temperatures. The bond between the base and the adjacent lamp portion may not be reliable over a long period of time. The cement is acidic; the acid therein, as well as remnants of solvents can corrode the current supply leads. It has already been tried to connect the ceramic sleeve to the pinch seal without cement--see, for example, U.S. Pat. No. 5,241,239, Rao. Manufacturing such lamps, however, is complex, time-consuming and expensive.